Protractor



Sebt. 22, 1931. G. H. DINGMAN PROTRACTOR Filed May 9. 1930 A llomey Patented Sept. 22, 1931 szaen GLEN H. DINGMAN, or GALNAsToTAQ NEW YORK Application filed May 9, 1e30, s ria uo; 4151,1146.

This invention relates to geometrical instruments and more particularly to new and useful improvements in protractors and has for its primary object to provide, in a manner as hereinafter set forth, a device of this char acter which will be comparatively simple in construction, strong, durable, etficient in its use and which may be manufactured at low cost.

All of the foregoing and still further objects and advantages of the invention may become apparent from a study of the following specification, taken in connection with the accompanying drawings wherein like characters of reference designate correspond-i ing parts throughout the several views, and wherein Figure 1 is a view in side elevation of a protractor constructed in accordance with as this invention.

fFigure 2 is a view in edge elevation there- 0 Referring to the drawings in detail, it will be seen that the reference numeral 1 designates a stationary or base arm having the straight edge 2, the stationary arm 1 is provided with a segmental recess 3 and a reduced inner end portion 4 having formed integrally thereon an ear or lug 5. so A fiat segmental plate 6 is rigidly secured to the stationary or base arm 1 and to the apertured ear 5 through the medium of suitable rivets 7, said plate extending transversely across the recess 3 as clearly illustrated in b Figure 1 of the drawings.

ginal portion of the segmental plate 6 is beveled, as indicated at 8 and said plate and arcuate marginal portion are graduated as indicated at 9. The numerals for the scale 9 comprise a double row which runs reversely from Zero to 90 as clearly seen in Figure 1. The segmental plate 6 is further provided with an arcuate slot 10.

A swinging arm 11 provided with a straight edge 12 has formed integrally on one end a substantially circular lug or extension 13 which is rotatably seated in the recess 3 and is disposed against one side of the segmen al plate 6 to which the same is rotatably secured through the medium of a suitable The arcuate mar- 3 pivot pin 14. The inner end of-the swinging arm=-l1 is provided :with a recess 15 for the reception ofthe aperturedfear or lug 5 011 theextension4 when the "said swinging arm 11' ls movedto open positions Within the open P08117101}, the inner end of the'swingingarm l-l is seated on the extension portion t of the stationary arm '1. 7' Ajthreaded screw 16 is rigidly mounted'on the swinging arm 11 and projects therefrom through the arcuate slot 10in the segmental. plate 6, said'screw adapted: to travel through saidslot upon swinging movement ofthe arm- I'l'. A thumb nut 17 is'threaded on the screw 16 for engagement with the adj acentspace of thesegmental plate 6 for frictionally-securing' the" swinging arm "11 in adjusted positions The arm 11 is further provided with an indicating'aarrow 18,which coacts with the scale- 9 to facilitate the use of the instrument. 3 29,,

As will be obvious, when itis desired to adjust the instrument the thumb nut 17'is loosened and the arm 11 is swung tothe desired angle, after which the thumb nut 17 is, again-tightened. 1 if I As before stated, when the swinging arm 11 I is movedto the limit of its outward swinging movement the inner end thereof abuts the inner-edge ofthe: reduced portion l of the stationary arm 1 and the apertured ear or 9 lug 5 -is disposed snugly in the recess 15 in the inner end ofsaidswinging arm 11; In this manner-an exceedingly strong-and durable instrument-is provided which is extremely simple in construction and efficient inits use. 3,,

*While the arms 1 and'll and the segmental graduated plate 6 may be formed of any suitable material, the same are preferably made pf (21L light transparent material such as cellu- 01 v 1 It 'isrbelieve d that themany advantages of a protractor constructed in accordance with this invention will be readily understood, and although the preferred embodiment of the invention is as illustrated and described, it &3 is to be understood that changes in the details of construction may be had which will fall within the scope of the invention as claimed.

What is claimed is f l. A protractor ofthe character described comprising a stationary arm formed to provide a straight edge and having a reduced end portion, said arm being further provided with an arcuate recess at the point where the 7 reduced portion merges therewith, an integral apertured ear projecting laterally from the reduced end portion, a flat, segmental plate rigidly securedto the stationary arm and'to the apertured ear, said plate being disposed across the recess, a swin able arm having an integral substantially circular extension on I one end portion, said extension being rotatably seated in the recess of the stationary arm, a pivot pin extending through the segmental plate and the substantially circular extension for swingably mounting the second named arm on the segmental plate, one end of the swingable arm'being engageable with the inner side edge of the reduced portion of the stationary arm and having a recess formed therein for the reception of the apertured ear when said swingable arm is in open position. 2. A protractor of the character described 7 comprising a stationary arm formed to provide a straight edge andhaving a reduced end portion, said stationary, arm being further. provided with an arcuate recess formed therein at the point Where the reducedend portion merges therewith, an integral ear projecting i at right angles from the-reduced portion, a

flat segmental plate rigidly secured to the stationary arm and to the ear, said plate extending across the, arcuate recess and having an arcuate slot therein, said plate being further provided with a graduated beveled arcu ate marginal portion, a swingable arm having a substantially circular'extension formed lat; erally on one end portion, said extension'being pivotally connected to the segmental plate on one side thereof and rotatably seated'in the arcuate recess of the stationary arm, a threaded screw anchored in the swingable arm and projecting therefrom through the slot in the segmental plate for movement therethrough upon swinging movement of said swingable arm, a thumb nut threaded on the screw for engagement with the segmental plate in a manner to frictionally secure the swingable arm in adjusted position, the pivoted end of the swingable arm being adapted to abut the adjacent longitudinal side edge of the re duced'portion of the stationary arm when in open position and having a recesstherein forthe reception of the ear. 7 5 In testimony whereof I aflix my signature.

GLEN H. DINGMAN. 

